The ‘Akohekohe (Palmeria dolei) is a critically endangered species that is restricted to less than 5% of its historical range. The primary threat to this species is avian malaria spread by introduced mosquitoes that can only persist in low and mid elevation (warmer) areas. Thus, ‘Akohekohe and other forest birds are restricted to high elevations where mosquitoes are absent. However, existing native forest at lower elevations may attract birds into areas where they may be exposed to disease. This can be described by the “ecological trap” theory wherein a habitat appears to be good for one reason (e.g. food) but is in fact poor for another reason (e.g. disease). This may be particularly true for juvenile birds without established home ranges.
In 2013 graduate student Alex Wang of the University of Hawai‘i – Hilo began a research project in conjunction with MFBRP to investigate the dispersal distance and direction (elevation) of juvenile ‘Akohekohe. Movement patterns of ‘Akohekohe were largely unknown and if juvenile birds are moving into disease-risk habitat then the juvenile life stage may prove to be a limiting factor for the species. As nectarivores ‘Akohekohe are highly dependent on constant sources of nectar. In native Hawaiian wet forests, the most common source of nectar for birds is the ʻōhiʻa tree. These trees bloom seasonally and an elevational gradient in the timing of the blooms has been recorded. In many places the highest densities of ʻōhiʻa blooms are found at high elevations in the cooler months and low elevations in the warmer months, at precisely the time when mosquitoes may also be able to reach higher elevations.
Alex and his crew used radio-telemetry to determine seasonal adult and juvenile movement patterns. A concurrent assessment of habitat quality via bloom intensity was conducted to test the hypothesis that ‘Akohekohe are subject to an “ecological trap” resulting from high ʻōhiʻa bloom in disease-risk low elevations. To document ‘Akohekohe movements and take foraging observations of both adults and juveniles, the team followed individual birds over the course of several weeks using radio telemetry. Radio telemetry uses a small transmitter to emit radio waves, which are then picked up by a receiver through an antenna. ‘Akohekohe were captured, color-banded, and a transmitter was placed on the bird like a small, temporary backpack. Each transmitter has its own frequency, like a radio station, and emits a beep to the receiver. To track the bird, the researcher used the antenna and the receiver, which was dialed in to a specific individual’s frequency. The researcher could then get close enough to each bird to read their color-bands and confirm their identity. In this way Alex and his team were able to record hourly and daily movements, monitoring its foraging and breeding habits as well.
A total of 29 ‘Akohekohe adults and juveniles were followed over two breeding seasons. Alex found that juveniles roamed over much larger areas than adults. The adults tended to stay in the same general area throughout the period, i.e. their “home range”. In contrast juvenile movement patterns were punctuated by long-distance flights followed by periods of stasis in a given area. These long-distance movements led a few individuals to briefly dip below the “mosquito line”, the theoretical elevational line above which mosquitoes cannot persist. Although the individuals that ventured lowest eventually returned to higher elevations, the propensity for juveniles to move such great distances, including downhill, strongly suggests that this age-class are likely at greatest risk for disease exposure. ʻŌhiʻa bloom density at higher elevations declined into the warmer months but did not increase during the spring and summer at lower elevations. However, a reduction in nectar sources at high elevations could theoretically lead to increased movement distance in search of food source.
Planning for this study started in 2011 and the pilot season began in 2013; research came to an end summer 2014. This research project was led by University of Hawai’i-Hilo graduate student Alex Wang and his adviser, Pat Hart.
If you are interested in becoming an MFBRP graduate student, please visit here.
Here is a presentation about this research:
Wang AX. 2015. Movement patterns of adult and juvenile ‘Akohekohe (Palmeria dolei). Presentation. Hawai’i Conservation Conference, Hilo, HI. View presentation here.
Conservation genetics is an interdisciplinary science that aims to apply genetic methods to the conservation and restoration of biodiversity. Genetic diversity is one of the three fundamental levels of biodiversity, so it is directly important in conservation of biodiversity, but genetic factors are also important in the conservation of individual species. Conservation of genetic variation is important to the overall health of populations because decreased genetic variability leads to increased levels of inbreeding, reduced fitness, and could accelerate species extinction.
Genetic diversity is the variability of genes in a species. It can estimate the mean levels of heterozygosity in a population. If genetic diversity becomes low at many genes of a species, that species becomes increasingly at risk. It has only one possible choice of information at all or nearly all of its genes’ ”in other words, all the individuals are nearly identical. If new pressures (such as environmental disasters) occur, a population with high genetic diversity has a greater chance of having at least some individuals with a genetic makeup that allows them to survive. If genetic diversity is very low, none of the individuals in a population may have the characteristics needed to cope with the new environmental conditions. Such a population could be suddenly wiped out.
Specific genetic techniques are used to assess the genetics of a species regarding specific conservation issues as well as general population structure. This analysis can be done in two ways, with current DNA of individuals or historic DNA. There are many techniques for analyzing the differences between individuals and populations.
Maui Forest Bird Recovery Project used microsatellites and mtDNA sequence data to analyze the current and historic population structure and diversity of the Kiwikiu (see Spatial genetic architecture of the critically-endangered Maui Parrotbill (Psuedonestor xanthophrys): management considerations for reintroduction strategies). These techniques provide information on the current diversity structure in the wild population and can be used to design knowledgeable management decisions for this species in the future.
This work was done in collaboration with UH Manoa in Hawaii and University of Kent in the UK, if you are interested in becoming an MFBRP graduate student, please visit here.
Due to extensive habitat destruction, the Maui ‘Alauahio (Paroreomyza montana) occurs in two known disjunct populations where habitat conditions vary extensively. The primary population occurs in wet and mesic montane native forests dominated by ʻōhiʻa (Metrosideros polymorpha). The second separate population occurs in non-native forests within Polipoli State Recreation Area or Kula Forest Reserve (see Field Sites). The Polipoli population lives in dry and mesic forests that were originally koa (Acacia koa.), mAmane (Sophora chrysophylla.) and ʻōhiʻa.However, after an experimental forest project in the 1930s it is now dominated by pine (Pinus spp.), eucalyptus (Eucalyptus spp.), ash (Fraxinus spp.), redwood (Sequoia spp.) and cedar (Thuja spp). These birds express differences in their behavior and ecology that have allowed them to exploit these new environments.
In 2013 graduate student Peter Motyka at Northern Arizona University in conjunction with MFBRP began research to investigate the use of non-native forest by native birds will facilitate the ability to evaluate the management of non-native forest for the benefit of native forest bird species. The objectives of this study were to: 1.) Conduct a multi-scale assessment of habitat use by the Maui ‘Alauahio in the Kula Forest Reserve; 2.) Determine the occurrence, distribution, and variable densities of Maui ‘Alauahio in the Kula Forest Reserve; 3.) Investigate potential correlations between bird occurrence and vegetation composition and structure; and 4.) Investigate home range and nesting substrates of Maui ‘Alauahio to determine habitat preference. The project included color-banding and resighting Maui ‘Alauahio, quantification of vegetation structure for foraging habits, variable circular plot point counts for bird densities, and nest searching and monitoring for Maui ‘Alauahio.
The remaining native forests on Maui are small and in order to prevent further extinctions conservation efforts need to consider the value of non-native, fragmented habitats as well. Current conservation efforts are focused on preservation and restoration, but the value of non-native forests for the conservation of native bird species may be of key importance. Many researchers have assessed the effects of forest fragmentation on avian populations but much of this work has focused on patch-level processes such as presence/absence and population turnover rather than demographic processes and there is a paucity of information on how non-native forest fragments are used by native species.
It is important to examine responses of species and ecosystems to landscape modification, and this can help lead to management strategies for natural ecosystem integrity in human-dominated ecosystems. This study advanced both our ability to make practical conservation recommendations as well as our perception of the potential for managing unnaturally altered habitat areas for the benefit and support of native species. The Maui ‘Alauahio is a native passerine under a high threat of extinction.
For more information, see the full thesis here.
This research project was led by Northern Arizona University graduate student Peter Motyka, advised by Dr. Jeffrey Foster.
If you are interested in becoming an MFBRP graduate student, please visit here.